/**
* Decrypt the contents of a file handle $inputHandle and store the results
* in $outputHandle using HKDF of $key to decrypt then verify
*
* @param resource $inputHandle
* @param resource $outputHandle
* @param Key $key
* @return boolean
*/
public static function decryptResource($inputHandle, $outputHandle, Key $key)
{
// Because we don't have strict typing in PHP 5
if (!\is_resource($inputHandle)) {
throw new Ex\InvalidInput('Input handle must be a resource!');
}
if (!\is_resource($outputHandle)) {
throw new Ex\InvalidInput('Output handle must be a resource!');
}
// Parse the header.
$header = self::readBytes($inputHandle, Core::HEADER_VERSION_SIZE);
$config = self::getFileVersionConfigFromHeader($header, Core::CURRENT_FILE_VERSION);
// Let's add this check before anything
if (!\in_array($config->hashFunctionName(), \hash_algos())) {
throw new Ex\CannotPerformOperationException('The specified hash function does not exist');
}
// Let's grab the file salt.
$file_salt = self::readBytes($inputHandle, $config->saltByteSize());
// For storing MACs of each buffer chunk
$macs = [];
/**
* 1. We need to decode some values from our files
*/
/**
* Let's split our keys
*
* $ekey -- Encryption Key -- used for AES
*/
$ekey = Core::HKDF($config->hashFunctionName(), $key->getRawBytes(), $config->keyByteSize(), $config->encryptionInfoString(), $file_salt, $config);
/**
* $akey -- Authentication Key -- used for HMAC
*/
$akey = Core::HKDF($config->hashFunctionName(), $key->getRawBytes(), $config->keyByteSize(), $config->authenticationInfoString(), $file_salt, $config);
/**
* Grab our IV from the encrypted message
*
* It should be the first N blocks of the file (N = 16)
*/
$ivsize = \openssl_cipher_iv_length($config->cipherMethod());
$iv = self::readBytes($inputHandle, $ivsize);
// How much do we increase the counter after each buffered encryption to prevent nonce reuse
$inc = $config->bufferByteSize() / $config->blockByteSize();
$thisIv = $iv;
/**
* Let's grab our MAC
*
* It should be the last N blocks of the file (N = 32)
*/
if (\fseek($inputHandle, -1 * $config->macByteSize(), SEEK_END) === false) {
throw new Ex\CannotPerformOperationException('Cannot seek to beginning of MAC within input file');
}
// Grab our last position of ciphertext before we read the MAC
$cipher_end = \ftell($inputHandle);
if ($cipher_end === false) {
throw new Ex\CannotPerformOperationException('Cannot read input file');
}
--$cipher_end;
// We need to subtract one
// We keep our MAC stored in this variable
$stored_mac = self::readBytes($inputHandle, $config->macByteSize());
/**
* We begin recalculating the HMAC for the entire file...
*/
$hmac = \hash_init($config->hashFunctionName(), HASH_HMAC, $akey);
if ($hmac === false) {
throw new Ex\CannotPerformOperationException('Cannot initialize a hash context');
}
/**
* Reset file pointer to the beginning of the file after the header
*/
if (\fseek($inputHandle, Core::HEADER_VERSION_SIZE, SEEK_SET) === false) {
throw new Ex\CannotPerformOperationException('Cannot read seek within input file');
}
/**
* Set it to the first non-salt and non-IV byte
*/
if (\fseek($inputHandle, $config->saltByteSize() + $ivsize, SEEK_CUR) === false) {
throw new Ex\CannotPerformOperationException('Cannot read seek input file to beginning of ciphertext');
}
/**
* 2. Let's recalculate the MAC
*/
/**
* Let's initialize our $hmac hasher with our Salt and IV
*/
\hash_update($hmac, $header);
\hash_update($hmac, $file_salt);
\hash_update($hmac, $iv);
$hmac2 = \hash_copy($hmac);
$break = false;
while (!$break) {
/**
* First, grab the current position
*/
$pos = \ftell($inputHandle);
if ($pos === false) {
throw new Ex\CannotPerformOperationException('Could not get current position in input file during decryption');
}
/**
* Would a full DBUFFER read put it past the end of the
* ciphertext? If so, only return a portion of the file.
*/
if ($pos + $config->bufferByteSize() >= $cipher_end) {
$break = true;
$read = self::readBytes($inputHandle, $cipher_end - $pos + 1);
} else {
$read = self::readBytes($inputHandle, $config->bufferByteSize());
}
if ($read === false) {
throw new Ex\CannotPerformOperationException('Could not read input file during decryption');
}
/**
* We're updating our HMAC and nothing else
*/
\hash_update($hmac, $read);
/**
* Store a MAC of each chunk
*/
$chunkMAC = \hash_copy($hmac);
if ($chunkMAC === false) {
throw new Ex\CannotPerformOperationException('Cannot duplicate a hash context');
}
$macs[] = \hash_final($chunkMAC);
}
/**
* We should now have enough data to generate an identical HMAC
*/
$finalHMAC = \hash_final($hmac, true);
/**
* 3. Did we match?
*/
if (!Core::hashEquals($finalHMAC, $stored_mac)) {
throw new Ex\InvalidCiphertextException('Message Authentication failure; tampering detected.');
}
/**
* 4. Okay, let's begin decrypting
*/
/**
* Return file pointer to the first non-header, non-IV byte in the file
*/
if (\fseek($inputHandle, $config->saltByteSize() + $ivsize + Core::HEADER_VERSION_SIZE, SEEK_SET) === false) {
throw new Ex\CannotPerformOperationException('Could not move the input file pointer during decryption');
}
/**
* Should we break the writing?
*/
$breakW = false;
/**
* This loop writes plaintext to the destination file:
*/
while (!$breakW) {
/**
* Get the current position
*/
$pos = \ftell($inputHandle);
if ($pos === false) {
throw new Ex\CannotPerformOperationException('Could not get current position in input file during decryption');
}
/**
* Would a full BUFFER read put it past the end of the
* ciphertext? If so, only return a portion of the file.
*/
if ($pos + $config->bufferByteSize() >= $cipher_end) {
$breakW = true;
$read = self::readBytes($inputHandle, $cipher_end - $pos + 1);
} else {
$read = self::readBytes($inputHandle, $config->bufferByteSize());
}
/**
* Recalculate the MAC, compare with the one stored in the $macs
* array to ensure attackers couldn't tamper with the file
* after MAC verification
*/
\hash_update($hmac2, $read);
$calcMAC = \hash_copy($hmac2);
if ($calcMAC === false) {
throw new Ex\CannotPerformOperationException('Cannot duplicate a hash context');
}
$calc = \hash_final($calcMAC);
if (empty($macs)) {
throw new Ex\InvalidCiphertextException('File was modified after MAC verification');
} elseif (!Core::hashEquals(\array_shift($macs), $calc)) {
throw new Ex\InvalidCiphertextException('File was modified after MAC verification');
}
$thisIv = Core::incrementCounter($thisIv, $inc, $config);
/**
* Perform the AES decryption. Decrypts the message.
*/
$decrypted = \openssl_decrypt($read, $config->cipherMethod(), $ekey, OPENSSL_RAW_DATA, $thisIv);
/**
* Test for decryption faulure
*/
if ($decrypted === false) {
throw new Ex\CannotPerformOperationException('OpenSSL decryption error');
}
/**
* Write the plaintext out to the output file
*/
self::writeBytes($outputHandle, $decrypted, Core::ourStrlen($decrypted));
}
return true;
}
/**
* Decrypts a file-backed resource with either a key or a password.
*
* @param resource $inputHandle
* @param resource $outputHandle
* @param KeyOrPassword $secret
*
* @throws Defuse\Crypto\Exception\EnvironmentIsBrokenException
* @throws Defuse\Crypto\Exception\IOException
* @throws Defuse\Crypto\Exception\WrongKeyOrModifiedCiphertextException
*/
public static function decryptResourceInternal($inputHandle, $outputHandle, KeyOrPassword $secret)
{
if (!\is_resource($inputHandle)) {
throw new Ex\IOException('Input handle must be a resource!');
}
if (!\is_resource($outputHandle)) {
throw new Ex\IOException('Output handle must be a resource!');
}
/* Make sure the file is big enough for all the reads we need to do. */
$stat = \fstat($inputHandle);
if ($stat['size'] < Core::MINIMUM_CIPHERTEXT_SIZE) {
throw new Ex\WrongKeyOrModifiedCiphertextException('Input file is too small to have been created by this library.');
}
/* Check the version header. */
$header = self::readBytes($inputHandle, Core::HEADER_VERSION_SIZE);
if ($header !== Core::CURRENT_VERSION) {
throw new Ex\WrongKeyOrModifiedCiphertextException('Bad version header.');
}
/* Get the salt. */
$file_salt = self::readBytes($inputHandle, Core::SALT_BYTE_SIZE);
/* Get the IV. */
$ivsize = Core::BLOCK_BYTE_SIZE;
$iv = self::readBytes($inputHandle, $ivsize);
/* Derive the authentication and encryption keys. */
$keys = $secret->deriveKeys($file_salt);
$ekey = $keys->getEncryptionKey();
$akey = $keys->getAuthenticationKey();
/* We'll store the MAC of each buffer-sized chunk as we verify the
* actual MAC, so that we can check them again when decrypting. */
$macs = [];
/* $thisIv will be incremented after each call to the decryption. */
$thisIv = $iv;
/* How many blocks do we encrypt at a time? We increment by this value. */
$inc = Core::BUFFER_BYTE_SIZE / Core::BLOCK_BYTE_SIZE;
/* Get the HMAC. */
if (\fseek($inputHandle, -1 * Core::MAC_BYTE_SIZE, SEEK_END) === false) {
throw new Ex\IOException('Cannot seek to beginning of MAC within input file');
}
/* Get the position of the last byte in the actual ciphertext. */
$cipher_end = \ftell($inputHandle);
if ($cipher_end === false) {
throw new Ex\IOException('Cannot read input file');
}
/* We have the position of the first byte of the HMAC. Go back by one. */
--$cipher_end;
/* Read the HMAC. */
$stored_mac = self::readBytes($inputHandle, Core::MAC_BYTE_SIZE);
/* Initialize a streaming HMAC state. */
$hmac = \hash_init(Core::HASH_FUNCTION_NAME, HASH_HMAC, $akey);
if ($hmac === false) {
throw new Ex\EnvironmentIsBrokenException('Cannot initialize a hash context');
}
/* Reset file pointer to the beginning of the file after the header */
if (\fseek($inputHandle, Core::HEADER_VERSION_SIZE, SEEK_SET) === false) {
throw new Ex\IOException('Cannot read seek within input file');
}
/* Seek to the start of the actual ciphertext. */
if (\fseek($inputHandle, Core::SALT_BYTE_SIZE + $ivsize, SEEK_CUR) === false) {
throw new Ex\IOException('Cannot seek input file to beginning of ciphertext');
}
/* PASS #1: Calculating the HMAC. */
\hash_update($hmac, $header);
\hash_update($hmac, $file_salt);
\hash_update($hmac, $iv);
$hmac2 = \hash_copy($hmac);
$break = false;
while (!$break) {
$pos = \ftell($inputHandle);
if ($pos === false) {
throw new Ex\IOException('Could not get current position in input file during decryption');
}
/* Read the next buffer-sized chunk (or less). */
if ($pos + Core::BUFFER_BYTE_SIZE >= $cipher_end) {
$break = true;
$read = self::readBytes($inputHandle, $cipher_end - $pos + 1);
} else {
$read = self::readBytes($inputHandle, Core::BUFFER_BYTE_SIZE);
}
/* Update the HMAC. */
\hash_update($hmac, $read);
/* Remember this buffer-sized chunk's HMAC. */
$chunk_mac = \hash_copy($hmac);
if ($chunk_mac === false) {
throw new Ex\EnvironmentIsBrokenException('Cannot duplicate a hash context');
}
$macs[] = \hash_final($chunk_mac);
}
/* Get the final HMAC, which should match the stored one. */
$final_mac = \hash_final($hmac, true);
/* Verify the HMAC. */
if (!Core::hashEquals($final_mac, $stored_mac)) {
throw new Ex\WrongKeyOrModifiedCiphertextException('Integrity check failed.');
}
/* PASS #2: Decrypt and write output. */
/* Rewind to the start of the actual ciphertext. */
if (\fseek($inputHandle, Core::SALT_BYTE_SIZE + $ivsize + Core::HEADER_VERSION_SIZE, SEEK_SET) === false) {
throw new Ex\IOException('Could not move the input file pointer during decryption');
}
$at_file_end = false;
while (!$at_file_end) {
$pos = \ftell($inputHandle);
if ($pos === false) {
throw new Ex\IOException('Could not get current position in input file during decryption');
}
/* Read the next buffer-sized chunk (or less). */
if ($pos + Core::BUFFER_BYTE_SIZE >= $cipher_end) {
$at_file_end = true;
$read = self::readBytes($inputHandle, $cipher_end - $pos + 1);
} else {
$read = self::readBytes($inputHandle, Core::BUFFER_BYTE_SIZE);
}
/* Recalculate the MAC (so far) and compare it with the one we
* remembered from pass #1 to ensure attackers didn't change the
* ciphertext after MAC verification. */
\hash_update($hmac2, $read);
$calc_mac = \hash_copy($hmac2);
if ($calc_mac === false) {
throw new Ex\EnvironmentIsBrokenException('Cannot duplicate a hash context');
}
$calc = \hash_final($calc_mac);
if (empty($macs)) {
throw new Ex\WrongKeyOrModifiedCiphertextException('File was modified after MAC verification');
} elseif (!Core::hashEquals(\array_shift($macs), $calc)) {
throw new Ex\WrongKeyOrModifiedCiphertextException('File was modified after MAC verification');
}
/* Decrypt this buffer-sized chunk. */
$decrypted = \openssl_decrypt($read, Core::CIPHER_METHOD, $ekey, OPENSSL_RAW_DATA, $thisIv);
if ($decrypted === false) {
throw new Ex\EnvironmentIsBrokenException('OpenSSL decryption error');
}
/* Write the plaintext to the output file. */
self::writeBytes($outputHandle, $decrypted, Core::ourStrlen($decrypted));
/* Increment the IV by the amount of blocks in a buffer. */
$thisIv = Core::incrementCounter($thisIv, $inc);
/* WARNING: Usually, unless the file is a multiple of the buffer
* size, $thisIv will contain an incorrect value here on the last
* iteration of this loop. */
}
}
